The present invention generally relates to supporting and securing printed board assemblies (PBA's) in electronic units. More particularly, the invention relates to supporting and securing the PBAs so that excess heat generated during operation of the PBAs may be effectively transferred away from the PBAs.
A typical electronic unit may include multiple PBAs positioned in an air-cooled enclosure. Connector jacks may be positioned at one end of the enclosure. A series of parallel elongated card guides may be positioned on an inside surface of the enclosure with each card guide being substantially aligned with one of the connector jacks. Upon assembly of one of the electronic units, a PBA may be slid into one of the card guides so that pin-connectors of the PBA are inserted into the connector jacks. Each of the PBAs may have one hundred or more pin-connectors. Therefore accurate alignment of the pin-connectors and the corresponding connector jacks must be attained so that the pin-connectors are not damaged during assembly of the electronic units.
A longitudinal locking device or retainer may be positioned between the PBA and its corresponding card guide. The retainer may be left in an unlocked condition during insertion of the PBA into the card guide. After the PBA is connected to the connector jack, the retainer may be locked so that it forces a portion of the PBA against a wall of the card guide. Thus, the retainer effectively prevents undesired movement of the PBA in the electronic unit. Additionally, because the retainer produces a clamping force between the PBA and card guide, a limited pathway for heat transfer from the PBA to the card guide may develop.
In many evolving application of electronic units, for example electronic units employed in modern aircraft and aerospace vehicle, there are conflicting design goals. On the one hand, there is a goal of building electronic units with higher power ratings. On the other hand, there is a goal of building electronic units with an overall smaller size and weight. These design goals translate into designs of electronic units with closely spaced PBAs and a need to transfer high amounts of excessive heat from the closely spaced PB
When PBAs are closely spaced, the card guides are narrow and the corresponding retainers are small. However, even though a retainer may be small, there is still a need that it remains effective in facilitating heat transfer from the PBA.
Additionally, electronic units with tightly spaced PBAs may be prone to pin damage during insertion of the PBAs unless very accurate alignment of the pin-connector and connectors jacks is maintained during insertion.
As can be seen, there is a need for a system of supporting and securing PBAs that provides effective heat transfer from closely spaced PBAs, and accurate alignment of pin-connectors of the PBAs with connector jacks of the electronic unit during insertion of the PBAs into an electronic unit.